随着计算机和通信技术的迅猛发展，大量敏感信息通过公共通信设施或计算机网络进行交换，特别是Internet的广泛应用、电子商务和电子政务的迅速发展，越来越多的个人信息需要严格保密，如银行账号、个人隐私等。正是这种对信息的机密性与真实性的需求，很有必要设计一个加密软件对其敏感信息加密。一个好的加密工具能够让用户方便快捷对重要信息进行有效保护，从而大大降低了公司的重要信息泄露的安全隐患，真正做到机密信息只供有权限的用户查阅。

本系统采用ASP.NET (C#)作为开发工具，系统主要功能包含：加密文件的密码设置、加密文件、解密密码的验证、解密文件等。加密功能需要扩展的方面有：对网络数据流加密和解密；对节点加密和节点解密；对数据打包封装，实现网络上使用密文传输；局部文本加密替换。此外，密钥的分配必须通过安全的渠道进行传输，因为密钥的管理是关系到整个加密方案的重要安全因素。

关键词：DES加密器；ASP.NET (C#)；文件加密；文件解密

The Implementation of a Document Encrypter Based on C#

With the rapid development of the computer and communication technologies， large mount of sensitive information are exchanged on the public communications facilities or computer networks. Especially under the situation of the widespread of the Internet applications， such as E-commerce and E-government， more and more information， such as bank account numbers， personal privacy， need to be encrypted. Such requirement for the secrecy and authenticity makes it necessary to develop an encrypter to encrypt the sensitive information.

This system， developed with ASP.NET (C #)， primarily includes such functions as setting the password of the document to be encrypted， encrypting the document， verifying the decryption password and decrypting the document. What needs to expand include encrypting and decrypting the network data or data on hosts; packaging data on the Internet and implementing encrypted transmission; replacing partial text in encrypted document. Besides， keys need to be transmitted on the safety channel because key management is the critical safety factor of the entire document. Users can protect their important data and prevent the unauthenticated persons from stealing the information by using the entrypter. Encryption is the key means to protect the important information， and decryption is to restore the encrypted data to make it readable.

Key words: The DES encrypter; ASP.NET ( C#); Document encryption; the Document decryption